from technet
Stand-alone primary site
- Up to 100,000 clients
- SQL Server is installed on the site server computer
- 8 cores (Intel Xeon E5504 or comparable CPU)
- 32 GB of RAM
- 550 GB hard disk space for the operating system, SQL Server, and all database files
Unless you are above 100k clients and need a CAS, installing SQL remotely on a single primary doesn't buy you anything. Plus, CM 2012 comes with a SQL standard license, so licensing isn't a factor.